Nasal mask and mask cushion therefor

ABSTRACT

A nasal cushion ( 30 ) comprises a substantially triangularly shaped frame ( 32 ) from which extends a membrane (34). The frame ( 32 ) has a scalloped edge ( 36 ) by which the cushion ( 30 ) is affixed to a A mask body. The membrane ( 34 ) has an aperture ( 38 ) into which the wearer&#39;s nose is received. The membrane ( 34 ) is spaced away from the rim ( 40 ) of the frame ( 32 ), and its outer surface ( 41 ) is of substantially the same shape as the rim ( 40 ). Respective notches ( 42, 44 ) receive the bridge of the wearer&#39;s nose. The wearer&#39;s nose is received through the aperture ( 38 ) into the chamber within the mask body ( 46 ). The seal forming portion ( 45 ) thus contacts both the surface of the wearer&#39;s nose and a portion of the wearer&#39;s face in the region between the base of the nose and the upper lip, and around the sides and over the bridge of the nose. The shape of the seal forming portion ( 45 ) is particularly suited to effectively seal the difficult region of the facial contour that is the crease between the sides of the nose and the face.

FIELD OF THE INVENTION

[0001] The invention relates generally to a nasal mask and to a cushiontherefor, for example, for use in the treatment of respiratoryconditions and in assisted respiration.

BACKGROUND OF THE INVENTION

[0002] Nasal masks are commonly used in the treatment of respiratoryconditions and sleep disorders (e.g., obstructive sleep apnea) bydelivering a flow of breathable gas for, or to assist patientrespiration. These nasal masks typically receive a gas supply line whichdelivers gas into a chamber formed by walls of the mask. The wallsusually are semi-rigid and have a face contacting portion including anaperture which is aligned with the wearer's nostrils. The facecontacting portion can comprisesa soft resilient elastomeric materialwhich may conform to various facial contours. The mask normally issecured to the wearer's head by straps. The straps are adjusted to pullthe mask against the face with sufficient force to achieve a gas tightseal between the mask and the wearer's face. Gas is thus delivered tothe mask and through the aperture to the wearer's nasal passages.

[0003] Problems often arise with masks of the above configuration. Forexample, the mask may be dislodged, thereby breaking the seal betweenthe mask and wearer. This may occur if the wearer rolls over whensleeping thereby creating a drag force on the gas supply line which istransmitted to the mask, breaking the seal. In the case of a mask beingused for the administration of Continuous Positive Airway Pressure(CPAP) treatment for the condition obstructive sleep apnea, such a leakcan result in the pressure supplied to the entrance of the wearer'sairway being below the Therapeutic value, and the treatment becomingineffective.

[0004] Another problem is that the face contacting portion may applyexcessive pressure to the wearer's face resulting in discomfort andpossibly skin irritation. This excessive forces. In some cases theseexcessive pressures and forces may cause the face to distort to conformwith the face contacting portion to increase wearer discomfort, facialsoreness and ulceration.

[0005] Other types of devices exist whereby small nostril nosepieces(pillows) are held in place by a harness strapped over the wearer'shead, for example as shown in prior art U.S. Pat. No. 4,782,832. Whilethis arrangement may alleviate some problems regarding seal breakage andskin abrasion, the harnesses associated with such devices are quitecumbersome for the wearer, as are the gas supply lines. Also, air‘jetting’ into the nostrils can be irritating to the patient making suchdevices generally uncomfortable to use.

[0006] In FIGS. 1-3, a prior art nasal cushion 10, generally equivalentto that shown in prior art U.S. Pat. No. 5,243,971, is first described.

[0007] As shown, the cushion 10 generally includes a base 11 from whichdepends a semirigid cushion frame 12 formed of elastomeric matenal.Attached over the outside of the frame 12 is a membrane 15, also ofelastomeric material, having at its distal end a face contacting portion14. The frame 12 and the membrane 15 generally form a chamber 17 intowhich the wearer's nose can be received. The frame 12 has a notch 19 toaccommodate the bridge of the wearer's nose. The base 11 includes slots13 to accomnodate straps (not shown) to secure the cushion 10 and a maskbody (not shown) in combination to the wearer's head.

[0008] An aperture 16 is formed at the end of the membrane 15 distalfrom the frame 12 providing access for a wearer's nose 20 to the chamber17 as noted. As shown, the aperture 16 in an unflexed state is generallycircular (or elliptical) and is large enough to allow partial entry ofthe wearer's nose. The resilience of the membrane material allows theface contacting portion 14 and the aperture 16 to invert when the noseis received. The inverted membrane arrangement relies upon a positivepressure of supplied gas within the mask to effect a seal to thewearer's face. The seal is characterised as a “rolling edge seal”, inthat there can be motion of the cushion 10 relative to the patient'sface yet the seal is maintained. Even so, a tuck 22 arises in thevicinity of the upper lip due to the circular shape of the aperture, andit is from this tuck that leaks can arise due to head and body movementduring sleep.

[0009] It is an object of the invention to overcome or at leastsubstantially ameliorate one or more of the foregoing disadvantages.

SUMMARY OF THE INVENTION

[0010] In one broad form, the invention discloses a nasal mask cushionto sealingly connect a mask to a wearer's face, the cushion comprising:

[0011] a substantially triangularly-shaped frame of resilient materialhaving a rim to surround the wearer's nose;

[0012] a membrane also of resilient material, the membrane beingrelatively more flexible than the frame, and being of the same generalshape as said rim and fixed to and extending away from the frame so asto have an outer surface spaced from the rim, a portion of said outersurface forming a face contacting seal; and

[0013] a nose-receiving cavity bounded by said frame and said membrane;

[0014] and wherein said seal portion is generally coterminous withrespect to said rim and is resiliently defotmable towards the rim in useof the cushion.

[0015] Preferably, the rim and seal portion are shaped to generallymatch facial contours of the facial tissue around the sides and over thebridge of the nose and between the base of the nose and the top lip.

[0016] In one particularly advantageous form, the membrane issubstantially saddle-shaped. The membrane further has a centrallylocated aperture through which the wearer's nose passes to enter saidcavity.

[0017] It is preferred that the cushion and membrane each include aco-located notch to accommodate the bridge of the nose of the wearer.Typically, the seal portion contacts at least dhe wearer's nose, andpreferably, also the facial tissue around the sides and over the bridgeof the nose and between the base of the nose and the top lip.

[0018] The invention further discloses a nasal mask for connection to awearer's face comprising:

[0019] a mask body for connection with a supply of breathable gas; and

[0020] a nasal cushion, the body and cushion defining a nose-receivingcavity, the cushion including:

[0021] a substantially triangularly-shaped frame of resilient materialhaving a rim to surround the wearer's nose;

[0022] a membrane also of resilient material, Me membrane beingrelatively more flexible than the frame, and being of the same generalshape as said rim and fixed to and extending away from tee frame so asto have an outer surface spaced from the frame, a portion of said outersurface forming a face contacting seal;

[0023] and wherein said seal portion is generally cotenminous withrespect to said rim and is resiliently deformable towards the rim in useof the mask.

[0024] The mask body can further include attachment points from whichsecuring straps can be attached, and by which the mask can be secured tothe wearer's head. The nasal mask can yet further comprise an armdepending from said body from which a further securing strap(s) can beattached.

[0025] The invention further discloses nasal CPAP treatment apparatuscomprising a flow generator for the supply of gas at a pressure elevatedabove atmospheric pressure to a gas delivery conduit, the conduit inturn coupled to a nasal mask as described mnmediately above.

[0026] In one particularly preferred form, a supply of gas can beprovided to said cavity, said supply of gas assisting, but not solelycausing maintenance of a seal by said seal forming portion of saidmembrane to the face of the wearer in use of the cushion.

[0027] Advantageously, because the membrane and the rim aresubstantially shaped to the facial contour, and the membrane does notneed to turn in on itself, as in the prior art, thus contacting the facewithout folds or creases. With the cushion/mask secured to the wearer'shead, the headstraps need only to be tensioned to balance the force dueto mask gas pressure that tends to lift the mask off the face. Suchrelatively lower maskto-face pressure results in.greater patientcomfort, and a reduction in the lilelihood of skin irritation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] An embodiment of the invention will now be described withreference to the accompanying drawings, in which:

[0029]FIG. 1 is an exploded perspective view of a prior art nasal mask;

[0030]FIG. 2 is a perspective view of the prior art nasal mask of FIG.1;

[0031]FIG. 3 is a perspective view of the prior art nasal mask attachedto a wearer;

[0032]FIG. 4 is a rear perspective view of a mask cushion embodying thepresent invention;

[0033]FIG. 5 is a cross-sectional view along line 5-5;

[0034]FIG. 6 is a perspective view of a nasal mask including the cushionof FIGS. 4 and 5; and

[0035]FIG. 7 is a perspective view of the nasal mask of FIG. 6 securedto a wearer's head.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036]FIG. 4 shows a perspective view of a nasal cushion 30 embodyingthe invention. FIG. 5 shows the cross-sectional view along line 5-5. Thecushion 30 comprises a substantially triangularly shaped frame 32 fromwhich extends a membrane 34. The frame 32 has a scalloped edge 36 bywhich the cushion 30 is affixed to a mask body, as presently will bedescribed.

[0037] The membrane 34 has an aperture 38 into which the wearer's noseis received in use of the cushion 30. The membrane 34 is spaced awayfrom the rim 40 of the frame 32, and its outer surface 41 is ofsubstantially the same shape as the rim 40. The outer surface 41 of themembrane 34 and the rim 40 of the frame 32 also can be described asgenerally saddle shaped. The shaping of the outer surface 41 of themembrane 34 and the rim 40 of the frame 32 also include respectivenotches 42,44 that receive the bridge of the wearer's nose in use of thecushion 30.

[0038] As is best seen in FIG. 5, the frame 32 and the membrane 34 areintegrally formed, typically by in a one-shot molding process. The frame32 and the membrane 34 are fabricated from a resilient material. Onesuitable such material is Silastic silicone elastomer manufactured byDow Corning. The frame 32, in one preferred embodiment, has a typicalthickness at its rim 40 of 1.5 mm. The membrane 34, in a preferredembodiment, has a typical thickness of 0.35 mm. In this way, themembrane 34 is relatively more flexible than the rim 40.

[0039] In use of the cushion 30, a wearer's nose will be inserted in theaperture 38 to engage a seal forming portion 45 (formed between thedashed lines) of the outer surface 41 to cause deformation of themembrane 34. Depending upon the securing force supplied to the membrane34, it may deform to a point where it butts against the rim 40 of theframe 32. The frame 32 has a rigidity sufficient to withstand usualsecuring pressures in use of the cushion 30 to tend to retain its shapeand resist deformation It thus acts as a supporting structure.

[0040] Referring now to FIG. 6, the nasal cushion 30 is shown attachedto a mask body 46 by the edge 36 of the frame 32, adhered or otherwisesecured to a flange 48 of dte mask body 46. Only the outer surface 41 ofthe membrane 34 can be seen. The flange 48 includes three slots 50-54from which tensioning straps can be attached to secure the cushion 30and the mask body 46 (in combination) to the head of a wearer.

[0041] The mask body 46 forms a cavity that can receive the nose of thewearer by the aperture 38. A port 56 is provided at the top of the maskbody 46 by which breathable gas can be supplied to the chamber.

[0042] Referring now to FIG. 7, there is shown a nasal mask 60 includingthe mask body 46 and the nsaak cushion 30. A coupling tube 62 isconnected at one end with the inlet port 56, and at the other to asocket 64 into which can be received a gas delivery tube (not shown) forthe supply of breathable gas to the chamber internal of the mask body46. The mask body 46 also has two vent openings 66 by which expired gasis exhausted. A first fastening strap 68 is fied between to the lowertwo slots 50,54. The upper slot 52 receives an arm 70, the top end ofwhich has a resilient pad 72 to engage the forehead of the wearer. Thearm 70 has two slots 74,76 along its side edges, by which a secondfastening strap 78 is secured.

[0043] In fitting the nasal mask 60, the wearer's nose is receivedthrough the aperture 38 into the chamber within the mask body 46. Theseal forming portion 45 thus contacts both the surface of the wearer'snose and a portion of the wearer's face in the region between the baseof the nose and the upper lip, and around the sides and over the bridgeof the nose. The shape of the seal forming portion 45 is particularlysuited to effectively seal the difficult region of the facial contourthat is the crease between the sides of the nose and the face. Dependingupon the tension applied by the fastening straps 68,78, a seal is formedwith the membrane 34 remaining spaced from the rimn 40 of the cushionframe 32. While the provision of pressurised gas to the chamber of themask body 46 assists in the maintenance of a seal between the membrane34 and the wearer's nose and face, it is not essential in most cases,and an effective seal will be formed absent any such pressurised gas.The seal formed between the membrane 34 and the wearer's nose and faceis not in the nature of a rolling seal in the manner of prior art asshown in FIGS. 1 to 3, as on relative movement of the mask 60 inrelation to the wearer's head, the nose will be restrained by contactingthe frame 32. Thus only limited relative motion between the mask 60 andthe wearer's nose and face occurs.

[0044] The membrane 34 closely imitates the facial contour, and becauseof its relatively lesser stiffness than the frame 32, can conform toparticular facial structures with minimum force, and without a tendencyto fold or crease.

[0045] If the fastening strap 68,78 are Visioned to excess, the membrane34 deforms to abut the rim 40 of the cushion 32, the frame 32 thusacting as an “end limit”. In such a configuration, almost zero relativemovement can occur between the mask 60 and the wearer's head.

[0046] The nasal cushion 30 and nasal mask 60 has been described withreference to CPAP or assisted respiration treatment, however it is to beunderstood that the invention generally is applicable to any applicationwhere gas and/or atoxised liquid is to be supplied to the entrance ofthe nasal airways. Such applications include nebulisers, gas masks andanaesthetic machines.

1. A nasal mask cushion to sealingly connect a mask to a wearer's face,the cushion comprising: a substantially triangularly-shaped frame ofresilient material having a rim to surround the wearer's nose; amembrane also of resilient material, the membrane being relatively moreflexible than the frame, and being of the same general shape as said rimand fixed to and extending away from the frame so as to have an outersurface spaced from the rim, a portion of said outer surface forming aface contacting seal; and a nose-receiving cavity bounded by said frameand said membrane; and wherein said seal portion is generallycoteriinous with respect to said rim and is resiliently deformabletowards the rim in use of the cushion.
 2. A nasal cushion as claimed inclaim 1, wherein said membrane and said rim each has a co-located notchto accommodate the bridge of a nose.
 3. A nasal cushion as claimed inclaim 1 or claim 2, wherein said membrane and said rim are substantiallysaddleshaped.
 4. A nasal cushion as claimed in claimn 3, wherein saidmembrane is shaped so that said seal portion, in use, contacts at leasta wearer's nose.
 5. A nasal cushion as clained in claim 4, wherein saidseal portion, in use, contacts the facial tissue around the sides andover the bridge of the nose, and between the base of the nose and thetop lip.
 6. A nasal cushion as claimed in claim 1, wherein said rim andsaid seal portion are shaped to generally match facial contours of thefacial tissue around the sides and over the bridge of the nose, andbetween the base of the nose and the top lip.
 7. A nasal mask forconnection to a wearer's face comprising: a mask body for connectionwith a supply of breathable gas; and a nasal cushion, the body andcushion defining a nose-receiving cavity, the cushion including asubstantially triangularly-shaped frame of resilient material having arim to surround the wearer's nose; a membrane also of resilientmaterial, the membrane being relatively more flexible than the frame,and being of the same general shape as said rim and fixed to andextending away from the frame so as to have an outer surface spaced fromthe frame, a portion of said outer surface forming a face contactingseal; and wherein said seal portion is generally coterminous withrespect to said rim and is resiliently deformable towards the rim in useof the mask.
 8. A nasal mask as claimed in claim 7, wherein said maskbody includes attachment points.
 9. A nasal mask as claimed in claim 8,rher comprising securing straps fixed to said attachment points.
 10. Anasal mask as claimed in claim 9, wherein said membrane and said rimeach has a co-located notch to accommodate the bridge of a nose.
 11. Anasal mask as claimed in claim 10, wherein said membrane and said rimare substantially saddleshaped.
 12. A nasal mask as claimed in claim 11,wherein said membrane is shaped so that said seal portion, in use,contacts at least a wearer's nose.
 13. A nasal mask as claimed in claim12, wherein said seal portion, in use, contacts the facial tissue aroundthe sides and over the bridge of the nose, and between the base of thenose and the top lip.
 14. A nasal mask as claimed in any one of claims7, 8 or 9, wherein said rhm and said seal portion are shaped togenerally match facial contours of the facial tissue around the sidesand over the bridge of the nose, and between the base of the nose andthe top lip.
 15. Nasal CPAP treatment apparatus comprising: a flowgenerator for the supply of gas at a pressure elevated above atmosphericpressure; a gas delivery conduit coupled to said flow generator; and anasal mask in turn coupled to said conduit to said nasal mask including:a mask body for connection with a supply of breathable gas; and a nasalcushion, the body and cushion defining a nose-receiving cavity, thecushion including: a substantially triangularly-shaped frame ofresilient material having a rim to surround the wearer's nose; amembrane also of resilient material, the membrane being relatively moreflexible than the frame, and being of the same general shape as said rimand fixed to and extending away from the frame so as to have an outersurface spaced from the frame, a portion of said outer surface forming aface contacting seal; and wherein said seal portion is generallycotenninous with respect to said rim and is resiliently deformabletowards the rim in use of tee mask.
 16. CPAP treatment apparatus asclaimed in claimn 15, wherein said mask body includes attachment points.17. CPAP treatment apparatus as claimed in claim 16, wherein furthercomprising securing straps fixed to said attachment points.
 18. CPAPtreatment apparams as claimed in claim 17, wherein said membrane andsaid rim each has a colocated notch to accommodate the bridge of a nose.19. CPAP treatment apparatus as claimed in claim 1, wherein saidmembrane and said rim are substantially saddle-shaped.
 20. CPAPtreatment apparams as claimed in claim 19, wherein said membrane isshaped so that said seal portion, in use, contacts at least a wearer'snose.
 21. CPAP treatment apparatus as claimed in claim 20, wherein saidseal portion, in use, contacts the facial tissue around the sides andover the bridge of the nose, and between the base of the nose and thetop lip.
 22. CPAP apparatus as claimed in any one of claims 15, 16 or 17wherein said rim and said seal portion are shaped to generally matchfacial contours of the facial tissue around the sides and over thebridge of the nose, and between the base of the nose and the top lip.